Caltrans investigates broken steel rods on new Bay Bridge

Failed bolts have been found in Pier E2, the pier on on the east-side of the Bay Bridge's single-anchored suspension span that ties down the road bed as it transitions to the conventional skyway. These photos are dated Nov 2, 2012. (Karl Mondon/Staff)

OAKLAND -- Bay Area transportation officials grilled Caltrans on Wednesday morning for answers to why nearly three dozen threaded steel rods -- 9 to 24 feet long -- on the new eastern span of the Bay Bridge snapped like pretzels.

"We want to assure the public that the bridge being constructed is safe," said Metropolitan Transportation Commission Chairwoman and Orinda Councilwoman Amy Worth following a detailed presentation. "It is very important that we have these briefings and we expect to hear from you (Caltrans) again."

Commissioners' questions ran the gamut, from the bridge's earthquake safety to who will pay the extra costs. They also wanted to know how defective rods came to be installed on the bridge in the first place.

The rods are not part of the span's day-to-day structural integrity and the state is confident engineers and American Bridge/Fluor Joint Venture will find a fix that leaves the bridge equally sound when the "Big One" hits, Caltrans Toll Bridge Program Manager Tony Anziano told the commission.

"This is one of many on a list of issues we have faced in the last decade of construction, so we are very optimistic that we will find a solution," Anziano said. The repairs are not expected to delay the scheduled Labor Day bridge opening.

Manufactured in Ohio, the rods are part of a set of seismic components designed to control the pier's movement during an earthquake. The pier -- a column anchored on the bay floor that supports the bridge -- is located just east of the self-anchored suspension span tower.

Advertisement

On the bridge, 288 three-inch thick rods of varying lengths were inserted into vertical holes in eight pre-cast seismic components called "shear keys" and "bearings" -- picture a block of wood with holes drilled out to make room for bolts. Those components were placed atop the pier before construction crews lowered the bridge deck in late 2011.

Workers then placed giant nuts on the threaded ends, which serve to clamp the shear keys and bearings sandwiched between the bridge deck and the top of the pier. The final nut tightening was done after the suspension span settled into position near the end of construction.

When crews tightened the 96 rods on two shear keys a few weeks ago, roughly a third broke under the pressure. Tightening of the remaining rods is on hold pending Caltrans' investigation.

Anziano suspects the defective rods contained excess levels of hydrogen, which weakens high-strength steel. Caltrans is investigating how and when the steel rods became brittle.

"Right now, we are focused on trying to find a solution," Heminger said. "But given the significant number of failures in the bolts, there was clearly a quality control problem. At some point, we will need to assign responsibility for the additional cost."

That cost has not yet been determined. In the meantime, the commission, state and contractor are exploring fixes.

The area where crews have already tightened down 96 rods pose the biggest repair challenge. The lower end is sealed and crews only have 5 feet of clearance on the top for rods that range from 9 feet to 24 feet long.

One possible solution is an external collar that would clamp the deck, shear keys and pier together, Anziano said. The remaining 192 rods that have not yet been tightened are accessible from the bottom of the pier cap and could be replaced, Anziano said.